1. Field of the Invention
The present invention relates to a wire grid polarizer, and a liquid crystal display device using the wire grid polarizer.
2. Related Background Art
The recent development of photolithography technique has enabled formation of a microstructural pattern with pitches of the level of the wavelength of light. Members and products with such extremely small pitches are of wide application and useful not only in the semiconductor field but also in the optical field.
For example, in a wire grid where wires comprised of metal and the like are arranged in the shape of a grid with specific pitches on a substrate, when the pitches are remarkably smaller than (for example, less than half) the incident light (for example, visible light with wavelengths of 400 nm to 800 nm), the wire grid reflects almost all the electric field vector component of the light vibrating in parallel with the wires, while allowing almost all the electric field vector component of the light perpendicular to the wires to pass through the grid, and is capable of being used as a polarizer to generate a polarized light beam. The wire grid polarizer reflects the light which is not passed through to be reused, and is desirable from the viewpoint of effective use of the light. However, in the existing photolithography technique, it has been difficult to implement a microstructural concavo-convex grid with pitches of the level of 120 nm or less in a large area of 100 cm2 or more.
In recent years, a wire grid polarizer has been developed which has a microstructural concavo-convex grid with small pitches (Japanese Patent Laid-Open No. 2003-502708). As shown in FIG. 10, the wire grid polarizer has a configuration where conductive elements 103 are formed via dielectric films 102 on grid-shaped convex portions 101a of a glass substrate 101. In the wire grid polarizer, the refractive index of a base portion X of the glass substrate 101 is set lower than the refractive index of a region Y with a thickness of the grid convex portion 101a and dielectric film 102. By preparing such a configuration, it is possible to shift to a short-wavelength region a resonance point of causing a resonance phenomenon such that transmission and reflection characteristics of the light rapidly change, and to improve the efficiency of transmission and reflection.
However, the above-mentioned wire grid polarizer needs to consider resonance in the visible light spectrum when the polarizer is used as a diffraction grating, and has a problem that a sufficient degree of polarization is not obtained in a short-wavelength region of the visible light.